JP3535901B2 - Orthogonal frequency division multiplex receiver - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Orthogonal Frequency Division Multiplexing receiver which is preferably implemented when receiving and using a digital audio broadcast which is modulated by a plurality of individual signals and multiplexed.

[0002]

2. Description of the Related Art In recent years, many digital communications have been put into practical use due to the great progress of digital technology. An example of these digital communications is digital audio broadcasting, which is a digitalization of radio audio broadcasting. In digital audio broadcasting, an audio signal that is an analog signal is converted into a digital signal, and digital signal transmission is performed from a broadcasting station to a general receiver.

Orthogonal Frequency Division Multiplexing, which is being developed in Europe, is one of the modulation methods used in digital audio broadcasting.
g; abbreviated as OFDM) method. In the OFDM method, a multiplex signal including a large number of individual signals which are digitized modulation signals to be communicated is divided into a large number of subcarriers arranged so as to be orthogonal to each other and assigned, and each subcarrier is assigned. In this method, signals are digitally modulated, and the digitally modulated subcarriers are multiplexed and transmitted. As the modulation method of each subcarrier,
Quadrature Phase Shift Keying (QP)
The system (abbreviated as SK) is most often used.

If the number of OFDM subcarriers is N, demodulation of the multiplexed signal basically requires N correlation detection means, but in practice, the discrete Fourier transform (D
A demodulation method using FT) is known, which allows demodulation of signals transmitted by N types of subcarriers at one time.

FIG. 7 is a block diagram showing the electrical configuration of an OFDM receiver using the conventional technique. In the conventional technique, the multiplexed signal received by the antenna 31 and the noise component included in the extra frequency band removed by the filter 32 is OFDM-demodulated by the OFDM demodulation means 33 to demodulate N parallel data signals. To be done. The N parallel data signals are converted into serial data by the parallel / serial conversion means 34, and the individual signal of the program selected and set by the user by the data setting means 36 is selected by the data selecting means 35 to generate a pulse. Coded Modulation (Pulse Code
Modulation; abbreviated as PCM) Decoder 37 demodulates the audio signal into an analog signal.

For example, "DAB-A new sound broa
dcasting system Status of the development−Routes t
o its introduction "(G.Plenge, EBU Review Technical
No. 246-APRIL 1991), the number of subcarriers N
, The bandwidth of the multiplexed signal OFDM-modulated using the subcarriers is about 1.5M.
It is said to be Hz. Since the filter 22 passes all the N types of subcarriers described above, its bandwidth is very wide. Therefore, the power of noise that filters the filter 22 increases. As described above, although the multiplex signal includes a plurality of individual signals, the P
The CM decoder 37 converts only one of the individual signals into an analog signal. Passing through all subcarriers as in the conventional technique reduces the CNR in the signal power to noise power (abbreviated as CNR) from the viewpoint of the subcarrier transmitting one individual signal, and the above q It becomes difficult to properly demodulate the individual signals.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to increase the CNR for one selected individual signal when demodulating a received multiplex signal so that a program can be listened to in a good reception state. Method receiver.

[0008]

The present invention modulates a total of N subcarriers with q individual signals and has a group (N = qm) of m q subcarriers. An orthogonal frequency division multiplex demodulation circuit for demodulating the multiplex signal to obtain data corresponding to a total of N types of subcarriers in an orthogonal frequency division multiplex system receiver for receiving and demodulating a multiplex signal in which signals are multiplexed; Data erasing means for selecting a predetermined individual signal from among the individual signals and erasing the data forming the selected individual signal, and orthogonal frequency division of the N types of subcarriers by the output of the data erasing means. Orthogonal frequency division multiplex modulation means for performing multiplex modulation, the orthogonal frequency division multiplex demodulation means for the multiplexed signal, the data erasing means, and the orthogonal frequency division multiplex modulation means. The delay unit for delaying by a predetermined time longer than the time required for the operation, the subtraction unit for subtracting and deriving the output of the orthogonal frequency division multiplexing modulation unit from the output of the delay unit, and the predetermined individual signal. An orthogonal frequency division multiplex system receiver including a filter that passes only m types of subcarriers having discrete frequencies corresponding to the data. Further, in the present invention, the frequency bandwidth in which the q types of subcarriers forming each group exist is set to a predetermined frequency bandwidth, and the filtering frequency band of the filter is the data forming the individual signal. And m frequency band portions respectively including the frequencies of the subcarriers, and the frequency bandwidth of the frequency band portion is selected to be less than the frequency bandwidth of the group. Further, the present invention is
The orthogonal frequency division multiplex system receiver receives a signal subjected to orthogonal frequency division multiplex modulation and filters the first bandpass filter, and outputs a local oscillation frequency signal. The local oscillation frequency signal has a variable frequency. An oscillation circuit and the first
A mixing circuit for mixing an output from the band-pass filter and an output from the local oscillator circuit, and a second band having a fixed filtering frequency band for obtaining one of the two beat frequency signals output from the mixing circuit. And receiving the signal by the super-heterodyne system, and applying the output from the second band filter to the orthogonal frequency division multiplexing demodulation circuit and the delay circuit.

[0009]

According to the present invention, a total of N types of subcarriers are modulated with q individual signals, and a signal having a group (N = qm) of m q types of subcarriers is multiplexed. An OFDM receiver that receives and demodulates a signal includes an orthogonal frequency division multiplexing demodulation circuit that demodulates the multiplexed signal to obtain data corresponding to a total of N types of subcarriers, and q individual signals in advance. A data erasing unit that selects a predetermined individual signal and erases the data that combines the selected individual signals, and an OF that performs OFDM modulation of N types of subcarriers by the output of the data erasing unit.
DM modulation means, delay means for delaying the multiplexed signal by a predetermined time longer than the time required for the operations of the OFDM demodulation means, the data erasing means and the OFDM modulation means, and the OFDM modulation from the output of the delay means. It includes a subtracting means for subtracting and deriving the output of the means, and a filter for passing only m kinds of subcarriers having discrete frequencies corresponding to the data forming the predetermined individual signal. Also, the OFDM receiver is
A first bandpass filter for receiving and filtering an FDM modulated signal; a local oscillator circuit for outputting a local oscillation frequency signal and varying the frequency of the local oscillation frequency signal; and an output from the first bandpass filter. A super-mixing circuit for mixing the output from the local oscillator circuit; and a second band-pass filter having a fixed filtering frequency band for obtaining a frequency signal of one of the two beat frequency signals output from the mixing circuit. The signal is received by the heterodyne method, and the output from the second band filter is transmitted to the OFDM demodulation circuit and the delay means. As a result, the predetermined individual signal can be extracted and demodulated by removing the influence of subcarriers other than the subcarriers that transmit the data signals forming the individual signal.

Further, according to the present invention, the frequency bandwidth in which the q types of subcarriers forming each group exist is set to a predetermined frequency bandwidth, and the filtering frequency band of the filter is the individual frequency band. M containing the frequencies of the subcarriers corresponding to the data forming the signal
Since the frequency bandwidth of the band portion is selected to be less than the frequency bandwidth of the group, it is not necessary that the filtering characteristic of the band portion is steep.

[0011]

1 is a block diagram showing the electrical construction of an OFDM receiver according to an embodiment of the present invention. The OFD
The M-system receiver includes an antenna 1, a first band filter 2, a mixer 3, a local oscillator circuit 4, an individual signal selection means 5, a second band filter 6, a delay means 7, an OFDM demodulation means 8, a data erasing means 9, It is configured to include an OFDM modulator 10, a subtractor 11, a filter 12, an OFDM demodulator 13, a parallel / serial converter 14 and a PCM decoder 15.

Generally, in digital modulation, q digitized individual signals are converted into a single digital signal by, for example, a time division multiplexing system. The time division multiplexing method narrows the pulse width of each individual signal and reduces the time position slightly so that the individual signals do not overlap in time when multiple individual signals are transmitted using one type of transmission path. This is a method of multiplexing the individual signals by shifting and superposing them. In the OFDM system, the multiplexed signal is divided into N types of subcarriers and assigned, and each subcarrier is modulated by the assigned digital signal.
Further, the modulated subcarriers are multiplexed and transmitted as one multiplexed signal. The subcarriers are arranged so as to be orthogonal to each other, and the center frequency thereof is an integral multiple of the fundamental frequency having the lowest center frequency among the N types of subcarriers. As a result, the symbol time, which is the time that can be used for the transmission of one data signal of the data signals that make up the digital signal, becomes longer, so that the effects of multipath interference and the like can be reduced.

FIG. 2 (1) schematically shows the spectrum structure of the multiplex signal. That is, when q individual signals are transmitted using N types of subcarriers, 1
One individual signal is transmitted using m = (N / q) types of subcarriers. The m types of subcarriers used are arranged at q type intervals. If the digital signal is a signal in which q individual signals are multiplexed by using a time division multiplexing method, the subcarrier is one of the data signals constituting the 1st to qth individual signals. One group includes m sets of q types of subcarriers each of which transmits one.

Consider, for example, extracting only the first individual signal. At this time, the signal derived by subtracting the signal obtained by removing the m types of subcarriers transmitting the data signal forming the first individual signal shown in FIG. 2B from the multiplexed signal shown in FIG. , (3) shown in FIG. 2 (3) is output as a signal composed of only m types of subcarriers for transmitting the data signal forming the first individual signal.

Referring again to FIG. The multiplex signal received by the antenna 1 has a noise component included in an extra frequency band in the first bandpass filter 2 having a filtering characteristic that allows only the multiplex signal to pass, as indicated by reference numeral 16 in FIG. 3 (1). The signal is removed, and as shown by reference numeral 17 in FIG. The local oscillation frequency signal output from the local oscillation circuit 4 is also input to the mixer 3. The above-mentioned multiplex signal shown in FIG. 3 (2) and the local oscillation frequency signal are mixed and converted into two beat frequency signals shown by reference numerals 18 and 19 in FIG. 3 (3). As will be described later, the local oscillation circuit 4 is controlled by the output from the individual signal selection means 5. Mixer 3
3 is filtered by a second band-pass filter 6 having a filtering characteristic that is shifted to the high frequency side by Δf from the beat frequency signal indicated by reference numeral 18 as shown in FIG. 3 (4). The output signal in which the 1st to (i-1) th subcarriers are missing from the beat frequency signal on the low frequency side of the two signals as shown by 21 is the delay unit 7 and the OFDM.
And demodulation means 8.

Frequency conversion of multiple signals using the superheterodyne system will be described with reference to FIG. As described above, the multiplexed signal having the center frequency f0 indicated by reference numeral 17 in FIG. 4 (1), which is received by the antenna 1 and filtered by the first band-pass filter 2, is the local signal of the frequency fL output from the local oscillator circuit 4. The oscillating frequency signal is multiplied by the mixer 3 and converted into two beat frequency signals whose center frequencies indicated by reference numerals 18 and 19 in FIG. 4 (2) are f0 ± fL. The two beat frequency signals are filtered by a second band-pass filter 6 having a filtering characteristic as shown by reference numeral 20 in FIG. Reference symbol 1 having a center frequency lower than the center frequency f0 of the multiplex signal
A multiplex signal having a center frequency f0-fL shown by 8 is selected.

In this way, the original multiplex signal and the local oscillation circuit 4
By mixing with the local oscillating frequency signal generated in, it is possible to obtain a signal having an intermediate frequency lower than the frequency of the original multiplex signal. Further, as will be described later, by arbitrarily changing the frequency fL of the local oscillation frequency signal, the center frequency of the output signal output from the mixer 3 can be set to an arbitrary value regardless of the frequency of the multiplex signal. it can.

Referring again to FIG. 1, the OFDM demodulation means OFDM demodulates the input output signal and demodulates N parallel data signals corresponding to N types of subcarriers. The N data signals are provided to the data erasing means 9. The data erasing means 9 is also supplied with the output from the individual signal selecting means 5. In the data erasing means 9, the data signal forming the predetermined individual signal in the individual signal selecting means 5 is converted into “0”. For example, when the first individual signal is selected, the data signal forming the first individual signal is expressed by the following equation.

Cn = 0 + j0 (n = 0, q, 2q, ..., (m-1) q) (1) In the OFDM modulation means 10, the subcarrier is OFDM-modulated by the output from the data erasing means 9. To be done. The subcarrier structure of the multiplexed signal at this time is, as shown by reference numeral 22 in FIG. 3 (6), for example, if the i-th individual signal is selected, the i-th subcarrier structure from the subcarrier structure shown by reference numeral 21 is selected. It has a configuration in which only subcarriers that transmit data signals that form individual signals are erased.

The OFDM modulation means 8 by the delay means 7,
Reference numeral 21 delayed by a predetermined time required for processing in the data erasing means 9 and the OFDM modulating means 10.
And the OFDM indicated by reference numeral 22.
The subtractor 11 subtracts the i-th modulated signal output from the modulator 10 from the erased signal and derives it. As shown in FIG. 3 (7), the derived signals include only m types of subcarriers that transmit data signals that form the individual signals predetermined by the individual signal selection means 5. The signal is filtered by a filter having a filtering characteristic indicated by reference numeral 24 in FIG.

FIG. 5 (1) shows the spectrum of the multiplexed signal modulated by the OFDM system. On the frequency axis, the multiple signals are overlapped while the spectra of the subcarriers indicated by reference numeral 28 are orthogonal to each other, and the whole becomes a rectangular spectrum as indicated by reference numeral 17 in FIG. 4 (1). There is. If the multiplexed signal is filtered by the filter 12 as it is and only the subcarriers transmitting the data signal forming one specific individual signal are to be taken out, the reference numeral of the filter 12 is changed as shown in FIG. 5 (2). Two
In the band portion, which is a part of the filtering band indicated by 4, the spectrum components of the adjacent subcarriers indicated by the reference numeral 26 in addition to the subcarrier indicated by the reference numeral 25 overlap and leak, so that the spectrum components of the adjacent subcarriers are leaked. Two
6 becomes a noise component, and the demodulation characteristic deteriorates. However, as described above, a signal indicated by reference numeral 23 in FIG. 5 (3) in which subcarrier components other than the required subcarriers are deleted in advance is created, and this signal is filtered by the filter 12 to obtain an extra portion. The part indicated by reference numeral 29 is excluded. In this case, since the spectrum component 26 of the adjacent subcarrier does not exist in each band portion 24 of the filter 12, the adverse effect of the adjacent subcarrier can be eliminated.

The relationship between the filtering characteristic of the second band filter 6 and the filtering characteristic of the filter 12 will be described below.

As described above, when the individual signal selecting means 5 selects the i-th individual signal, for example, in response to the output from the individual signal selecting means 5, the local oscillator circuit 4 causes the local oscillation circuit 4 to oscillate locally. Output a frequency signal. The frequency fL of the local oscillation frequency signal is expressed by the following equation.

[0024]

[Equation 1]

Here, fB1 is a predetermined arbitrary frequency. The multiplexed signal mixed with the local oscillation frequency signal is filtered by the second bandpass filter 6 as described above. Regarding the filtering characteristic of the second band-pass filter 6 indicated by reference numeral 20, the bandwidth indicated by reference numeral 27 is N / T and the center frequency is fB1 + (N / 2T). At this time, the frequency of the subcarrier having the lowest frequency among the m types of subcarriers transmitting the data signal forming the i-th individual signal is f0 + (i-1) / T. The frequency fb after frequency conversion of this subcarrier is expressed by the following equation.

[0026]

[Equation 2]

The frequency f of the local oscillation frequency signal
L is selected so that the frequency fb after the frequency conversion matches the predetermined arbitrary frequency fB1. The cutoff frequency of the second band filter 6 is set to fB1 on the low frequency side, and some of the subcarriers of the signal have a frequency less than fB1 and are not filtered. The aforementioned unfiltered subcarriers are
It is other than a subcarrier that transmits a data signal that constitutes the th individual signal, and does not affect the demodulation of the i th individual signal. A filter 1 for filtering a signal converted into a signal of only a subcarrier for transmitting a data signal forming the i-th individual signal by the subtractor 11.
The filtering characteristic of 2 has m discrete band parts, and the center frequency fBk of each band part is expressed by the following equation. Each said band part has the same bandwidth, eg 1 / T.

[0028]

[Equation 3]

The local oscillation frequency is adjusted so that each frequency-converted frequency of the m kinds of subcarriers transmitting the data signal forming the i-th individual signal coincides with the center frequency of each of the m band portions of the filter 12. The frequency fL of the signal is controlled. By using the second band filter 6 and the filter 12 whose filtering characteristics are fixed by this,
It is possible to filter the subcarriers carrying the data signals that make up any individual signal.

Referring again to FIG. The output from the filter 12 is given to the OFDM demodulation means 13 and the OFD.
M demodulation is performed to demodulate m parallel data signals. The m parallel data signals are converted into serial data by the parallel / serial conversion means 14,
An analog signal is demodulated by the M decoder 15, stereo demodulated by a stereo demodulation circuit, amplified by an amplification circuit, and output as a sound from a speaker.

When the QPSK method is used as the subcarrier modulation method, O per symbol time T
The FDM signal y (t) is expressed by the following equation.

[0032]

[Equation 4]

Here, Cn is the complex transmission signal alphabet which is the n-th data signal, that is, the amplitude of the transmission signal. fo is the transmission frequency, and the symbol "R
"e []" is a symbol indicating that the real part of the complex number in parentheses is taken. For example, when demodulating the first individual signal, the signal power Ps of the first individual signal is expressed by the following equation in consideration of the orthogonality of the subcarriers.

[0034]

[Equation 5]

In the prior art of FIG. 7, all data signals transmitted by the N types of subcarriers are OFDM-demodulated. Therefore, the bandwidth Bw of the bandpass filter that filters the signal received by the antenna has a frequency interval Δf1 = 1 / T.
A bandwidth that allows N kinds of subcarriers lined up every time to pass is required, and is expressed by the following equation.

Bw = N / T (7) At this time, the one-sided power spectrum density of the noise component is N0.
Then, the noise power PN after passing through the filter is
It is represented by.

[0037]       PN = N0 · Bw (8) Therefore, CNR is expressed by the following equation 9.

[0038]

[Equation 6]

As described above, in the prior art of FIG. 7, when demodulating a single individual signal, a filter capable of filtering all N types of subcarriers is used, so that the noise power PN becomes large. . Therefore, the CNR becomes small.

When a single individual signal to be output as voice, for example, only the first individual signal is taken out as in the embodiment of the present invention shown in FIG. 1, the band filter is as shown in FIG. 6 (2). The bandwidth BW1 of the band filter 12 having a filtering band composed of a plurality of narrow band parts arranged discretely and being the sum of the respective band parts is expressed by the following expression 10.

BW1 = m / T (10) The noise power PN1 after passing through the filter 12 is expressed by the following equation 11.

PN1 = N0.Bw1 = N0.m / T (11) The signal power of the first individual signal is equal to that in the case of using the above-described conventional technique of FIG. Therefore, if the CNR of the OFDM receiver of the present embodiment is CNR1, it is expressed by the following equation 12.

[0043]

[Equation 7]

Therefore, the improvement ratio ρ of CNR in the case of implementing this embodiment is expressed by the following equation 13.

[0045]

[Equation 8]

As described above, the CNR can be improved N / m times by extracting only one required individual signal.

In the embodiment shown in FIG. 1, the filter 12 shown in FIG.
Although a filter having a plurality of discrete band portions as shown in (8) is used, as another embodiment, a filter that passes only one subcarrier realized by a bandpass filter or the like is used as a center frequency interval. q /
You may use the thing arrange | positioned m for every T. A high-pass filter may be used instead of the band-pass filter having the minimum center frequency, and a low-pass filter such as a low-pass filter may be used instead of the maximum band-pass filter.

The high-frequency cutoff frequency of one band portion of the filter 12 may be increased to the extent that it does not exceed the low-frequency cutoff frequency of the adjacent band portion. On the contrary, the cutoff frequency on the low frequency side of the one band portion may be reduced to such an extent that it does not become lower than the cutoff frequency on the high frequency side of the adjacent band portion. When a plurality of filters as described above are used, the outputs of the filters may be added by an adder or the like and input to the OFDM demodulation means 13. Further, OFDM demodulation may be performed for each filter and the output thereof may be input to the parallel / serial conversion means 14. Further, each filter may be a digital filter or an analog filter.

When performing OFDM modulation and demodulation, a method using mathematical means such as DFT and inverse DFT is known, and the OFDM demodulation means 8 and 13 in FIG.
And the OFDM modulation means 10 is a DSP (Digital Sign).
al Processor) and the like. Also, OFDM
The demodulation means 8 and 13 calculate and obtain the correlation between the received digital value and a plurality of predetermined digital values, and adopt the predetermined digital value having the largest correlation value as the received digital value. It may be realized by N correlation detection means or the like for performing correlation detection.
The M modulation means 10 may be realized by N modulation means. Similarly, the delay means 7 may be realized by an analog delay line or the like, or may be realized by a DSP. DS
When P is used, the processing can be performed with high accuracy.

Furthermore, the individual signal to be demodulated may be predetermined or may be selected after demodulating a multiple signal. Further, the selection may be performed manually, or may be performed automatically in consideration of noise of the demodulated signal and the like.

[0051]

As described above, according to the present invention, OFDM for receiving and demodulating a multiplexed signal in which signals having a total of m groups in which a total of N types of subcarriers are modulated with q individual signals are multiplexed are received. A system receiver demodulates the multiplexed signal to obtain data corresponding to a total of N types of subcarriers.
An FDM demodulation means, a data erasing means for selecting a predetermined individual signal from the q individual signals, and erasing the data forming the selected individual signal, and an N output by the data erasing means. OFDM modulation means for performing OFDM modulation on a subcarrier of a kind, delay means for delaying the multiplex signal by a predetermined time that is equal to or longer than the time required for the operation up to the OFDM demodulation means, the data erasing means and the OFDM modulation means, Subtracting means for subtracting and deriving the output of the OFDM modulating means from the output of the delaying means, and filters for respectively passing only m kinds of discrete frequencies corresponding to the data forming the predetermined individual signal. According to the invention, the O
The FDM receiver includes a first bandpass filter that receives and filters an OFDM-modulated signal, a local oscillation circuit that outputs a local oscillation frequency signal, and a frequency of the local oscillation frequency signal is variable, and the first bandpass filter. A mixing circuit that mixes the output from the filter and the output from the local oscillator circuit, and a second band-pass filter with a fixed filtering frequency that obtains one of the two beat frequency signals output from the mixing circuit. And receiving by the super-heterodyne system, and giving the output from the second band filter to the OFDM demodulation means and the delay means. As a result, the predetermined individual signal can be taken out and demodulated by removing the influence of subcarriers other than the subcarriers that transmit the data signals forming the individual signal. Therefore, the CNR can be increased, and the individual signal can be demodulated as a good signal with less noise.

Further, according to the present invention, the frequency bandwidth in which the q types of subcarriers forming each group exist is set to a predetermined frequency bandwidth, and the filtering frequency band of the filter is the selected frequency band. The frequency band width of the band portion is selected to be less than the frequency bandwidth of the group. It is not necessary to make the filtering characteristics steep. This can facilitate the design of the filter.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an OFDM receiver according to an embodiment of the present invention.

FIG. 2 is a simplified waveform diagram for explaining a spectrum configuration of a multiplexed signal.

3 is a simplified waveform diagram for explaining the operation of the OFDM receiver of FIG.

FIG. 4 is a graph for explaining frequency conversion using the mixer 3, the local oscillator circuit 4, and the second band filter 6.

FIG. 5 is a waveform diagram showing a spectrum configuration of a multiplexed signal.

FIG. 6 is a graph showing the relationship between the bandwidths of the second band filter 6 and the filter 12 and their center frequencies.

FIG. 7 is a block diagram showing an electrical configuration of an OFDM receiver using a conventional technique.

[Explanation of symbols]

1 antenna 2 First band filter 3 mixer 4 local oscillator 5 Individual signal selection means 6 Second band filter 7 delay means 8,13 OFDM demodulation means 9 Data erasing means 10 OFDM Modulating Means 11 Subtractor 12 filters 14 Parallel / serial conversion means 15 PCM decoder

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04J 11/00 H04B 1/10 H04B 1/16

Claims (3)

(57) [Claims] 1. A multiplex signal obtained by modulating a total of N types of subcarriers with q individual signals and multiplexing a signal having a group (N = qm) of m number of the subcarriers. In the orthogonal frequency division multiplexing receiver for demodulation, an orthogonal frequency division multiplex demodulation circuit that demodulates the multiplex signal to obtain data corresponding to a total of N types of subcarriers, and q individual signals in advance Data erasing means for selecting an individual signal to be defined and erasing the data constituting the selected individual signal, and orthogonal frequency division multiplex modulation for orthogonal frequency division multiplex modulation of the N types of subcarriers by the output of the data erasing means. Means for performing the operation of the orthogonal frequency division multiplex demodulation means, the data erasing means, and the orthogonal frequency division multiplex modulation means for the multiplexed signal, Of delaying means for delaying by a predetermined time, subtracting means for subtracting and deriving the output of the orthogonal frequency division multiplexing modulation means from the output of the delaying means, and m kinds corresponding to the data forming the predetermined individual signal. Orthogonal frequency division multiplexing receiver including a filter that passes only subcarriers of discrete frequencies of. 2. A frequency bandwidth in which q kinds of subcarriers forming each group exist is set to a predetermined frequency bandwidth, and a filtering frequency band of the filter is a data forming the individual signal. Have m band portions each containing the frequency of the subcarrier corresponding to
The orthogonal frequency division multiplexing receiver according to claim 1, wherein the frequency bandwidth of the band portion is selected to be less than the frequency bandwidth of the group. 3. The orthogonal frequency division multiplexing receiver includes a first band-pass filter for receiving and filtering an orthogonal frequency division multiplex modulated signal, a local oscillation frequency signal, and a frequency of the local oscillation frequency signal. , A mixing circuit that mixes the output from the first band filter and the output from the local oscillation circuit, and one of the two beat frequency signals output from the mixing circuit. The second fixed frequency band for obtaining
3. A band-pass filter, which is received by a super-heterodyne system, and which outputs the output from the second band-pass filter to the orthogonal frequency division multiplexing demodulation circuit and the delay circuit. An orthogonal frequency division multiplexing receiver as described.